The resistance and sensitivity of piezo-resistive bridges vary significantly with temperature. As a result, the signal output of piezo-resistive bridges varies significantly as a function of temperature. Customarily, the bridge resistance variation is used to passively vary the bridge excitation to normalize the signal output. A common method of compensation is to place a resistance in series with the bridge. This compensation occurs because the bridge resistance increases as the temperature increases. As a result, the excitation of the bridge increases which compensates for the loss of bridge sensitivity from increasing temperature. However, to achieve self-compensation, a resistance used in series with the bridge can waste about two-thirds of the available power supply voltage. In addition to wasting the bridge excitation voltage, this compensation is not usable over a wide temperature range because it is non-linear. Usually a micro-controller based ASIC is used to provide a matching non-linear signal path to achieve compensation over a wider temperature range. However, micro-controllers are cost prohibitive in most aerospace pressure sensor applications because of the DO-178 software certification requirements. Likewise an ASIC would need DO-254 certification and would likely lead to obsolescence issues in the 40 year long life cycles encountered in the aerospace industry.
What would be desirable is a non-linear compensation system that attenuates the waste of the available power supply voltage and achieves a compensation over a wider temperature range without the use of micro-controllers or ASICs.